text: The C/EBPα, C/EBPβ, C/EBPγ and C/EBPδ genes are without introns. C/EBPζ has four exons; C/EBPε has two, which lead to four isoforms due to an alternative use of promoters and splicing. For C/EBPα and C/EBPβ, different sizes of polypeptides can be produced by alternative use of initiation codons. This is thought to be due to weak ribosome scanning mechanisms. The mRNA of C/EBPα can transcribe into two polypeptides. For C/EBPβ, three different polypeptides are made: LAP* (38 kDa), LAP (35 kDa) and LIP (20 kDa). The most translated isoform is LAP, then LAP* and LIP. LIP can act as an inhibitor of the other C/EBPs by forming non-functional heterodimers.